Multi point sash lock systems and multi point door lock systems are known. These systems typically have a single operating control, usually a lever or door knob. The operating control is linked to a tie bar that allows activation of the remote locking points in addition to the main locking point. Operation of the lever or knob causes the tie bar to move longitudinally, generally along the long axis of the window or the door. Tie bar guides are used to secure the tie bar to the sash or door preventing transverse movement of the tie bar while permitting the tie bar to move longitudinally.
Increasingly, self locating tie bar guides are utilized when tie bars are installed in casement windows. Self locating tie guide bars simplify the construction and assembly of casement windows and doors. Self locating tie bar guides are prepositioned at desired locations along the length of the tie bar until they are secured, typically by screws, to the sash, window frame or door. Self locating tie bar guides eliminate the need to either pre-drill holes that locate the guide securing screws or to build jigs or fixtures to hold the guides in place during the assembly process. They thus facilitate and speed assembly of the locking mechanism with the window or door.
There are several tie bar systems that have self locating tie bar guides. Self locating tie bar guides are positioned along the tie bar at predefined locations and are secured to the tie bar in such a way as to stay in position until the tie bar guides are secured to the sash and the mechanism is operated.
There are generally two types of self locating tie bar guides. First, are those that include a tab pin or some other feature that is frangible and that is broken off when the lock is operated for the first time and the tie bar is moved longitudinally. Second are those that have a detent feature that is engaged and disengaged every time the lock is operated. Each of these designs has certain short comings.
In systems that require a feature to be broken with the first operational cycle of the lock, the lock can be difficult to operate on the first cycle because sufficient force must be applied to sever the breakable feature. This is especially true when multiple locking points are used. Very often, the first operator of the lock is a homeowner. Homeowners commonly assume that there is something wrong with the window when it is difficult to operate the lock mechanism the first time. Alternately, they may believe that a part of the lock mechanism not intended to break has been broken when they initially operate the lock. This can lead to increased warranty claims and dissatisfaction on the part of the homeowner.
An additional concern that arises with systems that have a breakable feature, is that a broken off piece, when it is separated, can become free and lodge in some moving part of the lock mechanism. This can cause binding, noise or other problems which can also lead to increased warranty claims and homeowner dissatisfaction.
In the case of systems that have a permanent detent feature which engages and disengages every time the lock is operated, the detent can be felt every time the locked is cycled. This prevents smooth operation of the lock hardware which is generally desirable.
One example of prior art breakaway pin designs includes a tab on a plastic tie bar guide that engages in a notch on the steel tie bar to position the guide. The tab breaks away when the lock is first cycled. Another example of a prior art tie bar system uses a small tab to hold a t-shaped guide into a c-shaped tie bar. When the tie bar guide is secured with a screw, a shoulder of the mounting screw pushes the location tab into a recess in the tie bar guide. This allows the tie bar to slide freely once installed.
Another prior art approach uses a leg with a post that fits into a hole in the tie bar guide. When the lock is first cycled, the post is forced out of the hole by movement of the tie bar and forces the leg upward. This causes the leg to yield or break at a weak point built into the leg. After the material of the leg has yielded, there is no downward pressure on the post and the post does not reengage into the hole, thereby freeing the tie bar for use. Another prior art device includes a dual tie bar guide with a breaking tab. The tab is fastened to the tie bar at a lock roller rivet. When the lock is operated for the first time, two small attachment points break allowing the tie bar to travel freely. The tab remains attached to the tie bar.
Accordingly, there is still room for improvement in the design of self locating tie bar guides.